Comparison of calcium hydroxide removal by self-adjusting file, EndoVac, and CanalBrush agitation techniques: An in vitro study.

OBJECTIVES: This study comparatively evaluated the efficacy of self-adjusting file (SAF), Endovac, and CanalBrush irrigant agitation protocols in removing calcium hydroxide (Ca(OH)2) from the root canals.
MATERIALS AND METHODS: Sixty extracted human mandibular canine teeth were instrumented with ProTaper rotary instruments to size #40 and dressed with Ca(OH)2. The roots were randomly assigned to four groups according to irrigant agitation protocol used (n = 15). In Group 1: Conventional syringe irrigation (no activation, control); Group 2: Rotary brush agitation (CanalBrush); Group 3: Apical negative pressure irrigation (EndoVac system); and Group 4: Sonic agitation (SAF) were used. Scanning electron microscopic (SEM) evaluation was done for assessment of Ca(OH)2 removal in the coronal and apical thirds. Statistical analysis was performed by Wilcoxon and Kruskal-Wallis tests.
RESULTS: There were statistically significant differences among the groups (P = 0.218). A statistically significant difference was seen between the test groups in Ca(OH)2 removal from the apical third of the canal (P < 0.05). In the coronal third, there was no difference between the groups (P > 0.05). The most efficient Ca(OH)2 removal in apical third was recorded in Group 3 (EndoVac) and Group 4 (SAF) (P < 0.05). In Group 4 (sonic agitation), there was no significantly difference between Ca(OH)2 removal in coronal and apical thirds.
CONCLUSIONS: SAF and EndoVac showed significantly better performance than CanalBrush and conventional syringe irrigation in removing Ca(OH)2 from apical third of the root canals.

INTRODUCTION

The presence of microorganisms in the root canal system plays a fundamental role in the pathogenesis of apical periodontitis.[1] The elimination of all microorganisms from the root canal system is accomplished by mechanical instrumentation supported by various irrigating solutions and placement of intracanal medications.[2] Calcium hydroxide (Ca(OH)2) is a commonly used intracanal medicament because of its proven antimicrobial activity,[3] for its capacity to neutralize bacterial endotoxin[4] and stimulate apical and periapical repair.[5] Ca(OH)2 paste should be removed before the obturation of root canal because the remnants of Ca(OH)2 on the canal walls influence dentine bond strength[6] and negatively affect the quality of root filling.[7] The main drawback of removing Ca(OH)2 residues is irregularities on the root canal walls.[8] Sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) irrigation solutions are commonly used for the removal of residual Ca(OH)2.[9] Passive ultrasonic irrigation (PUI),[10] rotary nickel titanium instruments,[11] and apical patency file[12] have been used to activate the effectiveness of irrigants. Although various irrigants and methods have been proposed for the removal of Ca(OH)2 dressing, there is still no general consensus about which technique is best.

The EndoVac system (Discus Dental, Culver City, CA, USA) was newly introduced and designed to safely deliver irrigants to the apical terminus of root canals. The recommended protocol for the use of apical negative pressure irrigation includes two main phases: Macro- and microirrigation. This system is composed by a macro- and microcannula that make the irrigating solution circulate due to difference of pressure caused by the vacuum inside the root canal system.[13] Measuring 0.32 mm in diameter, the microcannula can be placed to the working length (WL), provided the canal is prepared to a minimum size specified by the International Organization for Standardization 35.

The other new branch is represented by the self-adjusting file (SAF) system which is a hollow file designed as a compressible, thin-walled, pointed cylinder 1.5 mm in diameter; and composed of 120 μm thick nickel-titanium lattice. It is operated with a continuous flow of NaOCl that is delivered into the root canal through the hollow file and claimed to be activated by sonic agitation of the irrigant.[14]

No study has compared the Ca(OH)2 removal efficacy of SAF with Endovac and CanalBrush. The purpose of this study was to compare the efficacy of SAF with EndoVac and CanalBrush in removing Ca(OH)2 from root canal walls.

MATERIALS AND METHODS

Sixty freshly extracted human mandibular canine teeth with intact mature apices were used for evaluation. All teeth were single rooted with a single canal, which was confirmed with multiple angulated radiographs. Following extraction, teeth were scaled with ultrasonic instruments, washed with distilled water, and immersed in 10% formalin solution until use. The crowns were removed at the cementoenamel junction with a water-cooled diamond disc (KG Sorensen, Barueri, SP, Brazil) at low speed to obtain a standardized root length of 15 mm. A size 15 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was passively introduced into each canal until its tip was just visible at the apical foramen. The WL was established by subtracting 1 mm from this length. All canals were prepared by the same operator using ProTaper nickel-titanium rotary instruments (Dentsply Maillefer, Baillagues, Switzerland) to size #40 as the master apical file. During the preparation, the root canal was irrigated with 2 mL of 2.5% NaOCl solution after each instrument. The irrigant was delivered via a 27-gauge needle, which was placed passively into the canal, up to 3 mm from the apical foramen without binding. When instrumentation was completed, final irrigation was applied using 5 mL 17% EDTA and 5 mL 2.5% NaOCl and then dried with paper points. Ca(OH)2 (Calcicur, Voco, Cuxhaven, Germany) was placed into each canal via a lentulo spiral to the WL until the medicament was visible at the apical foramen. The access cavities were sealed with cotton pellet and temporary filling (Cavit, ESPE, Seefeld, Germany). All samples were stored at 37 ± 1°C and 100% relative humidity for 7 days.

Sixty specimens were randomly assigned into four experimental groups based on irrigant agitation protocols (n = 15). Initially, a size #40 Hedström file was inserted into the root canals to the WL and up and down strokes were performed to disrupt and loosen the medication. The groups were as follows: In Group 1, conventional syringe irrigation (no activation): 27-gauge conventional irrigation needle was inserted as deep apically as possible without binding, and irrigation was performed with 10 mL of 2.5% NaOCl solution; in Group 2, root canals were irrigated with 5 mL of 2.5% NaOCl, and a medium-sized CanalBrush (Coltène/Whaledent, Langenau, Germany) was placed in a slow-speed handpiece (600 rpm) and advanced to the WL. CanalBrush was applied into the canals for 30 s with circumferential motion, and a final irrigation of 5 mL of 2.5% NaOCl was used. One CanalBrush per root was used. The brush was used at full WL with a gentle up and down motion.

In Group 3, the Apical Negative Pressure Irrigation (EndoVac, Discus Dental, Culver City, CA) was used. The macrocannula tip was used to deliver irrigant up and down the canal for 1 min. This was followed by three cycles of microcannula irrigation. Each cycle of microcannula irrigation consisted of the tip being placed at full WL for 6 s and then withdrawn 2 mm from full WL for 6 s. This was repeated five times during a period of 30 s. A total of 10 mL of 2.5% NaOCl was used.

In Group 4, SAF (Redent-Nova, Ra’anana, Israel) with 2.0 mm diameter and 25 mm length was operated in the canal using an RDT3 NX handpiece head (Re-Dent Nova, Ra’anana, Israel) with endodontic motor (X-Smart, Dentsply Maillefer, Ballaigues, Switzerland), that produced 5,000 vibrations per min with an amplitude of 0.4 mm. The SAF was used for 4 min with 2.5% NaOCl at a flow rate of 2.5 mL/min.

After the irrigation procedures, the canals were dried with paper points, and longitudinal grooves were prepared on the buccal and lingual surfaces of each root with a diamond disk at a slow speed without penetrating the canal. The teeth were split along their long axis in a buccolingual direction using a hammer and chisel. For scanning electron microscopic (Quanta 400F Field Emission SEM, FEI, Oregon, USA) analysis, the samples were dehydrated and coated with gold-palladium particles, and a magnification of 1,000× was used to evaluate the cleanliness of the canal walls at the apical andcoronal thirds of root canal. The images of canal surfaces were selected from apical and coronal thirds (3 and 11 mm shorter from the apex, respectively) for SEM evaluation. A scoring system, which was previously described by Kuga et al.,[11] was used to evaluate the quantity of remnants on the canal walls. The scores used were as follows: Score 0: Absence of residues, score 1: Small amount of residues (up to 20% of the surface covered), score 2: Moderate amount of residues (20-60% of the surface covered), score 3: Large amount of residues (more than 60% of the surface covered).

All Ca(OH)2 removing procedures were completed by one operator and SEM evaluations were performed by a second examiner who was blind in respect of test groups. Statistical analysis was performed by Wilcoxon and Kruskal-Wallis tests. All statistical tests were performed using the software, Statistical Packages for Social Sciences (SPSS), version 19.0 for Windows (SPSS Inc., Chicago, IL). A value of P < 0.05 was considered statistically significant.

RESULTS

Sample SEM images of apical and coronal thirds of each group were shown in Figure 1. The mean scores and standard deviations (SDs) for the coronal and apical thirds of groups were shown in Tables 1 and 2, respectively. Comparing the irrigant agitation protocols with respect to Ca(OH)2 removal, all irrigant agitation protocols successfully removed Ca(OH)2 at the coronal third. No statistically significant difference (P > 0.05) was found among the irrigant agitation protocols at the coronal third. Group 1 (no activation) demonstrated the highest score values, but it was not statistically different from other groups. Whereas, Group 3 (apical negative pressure irrigation) and Group 4 (Sonic agitation) demonstrated the lowest scores in coronal thirds. At the apical third, Group 1 (no activation) demonstrated highest score values. No difference was found between Groups 1 (no activation) and 2 (rotary brush agitation). Groups 3 (apical negative pressure irrigation) and 4 (sonic agitation) were significantly efficient for the removal of Ca(OH)2 at the apical third in comparison with Groups 1 and 2 (P < 0.05). In Group 4 (sonic agitation), there was no significant difference between Ca(OH)2 removal in coronal and apical thirds.

Figure 1

Scanning electron microscopy images of the coronal and apical thirds in each group

Table 1

The mean scores and standard deviations of the coronal thirds. A different superscript in the column of mean values indicates statistically significant different values

Table 2

The mean scores and standard deviation (SD) of the apical thirds. A different superscript in the column of mean values indicates statistically significant different values

DISCUSSION

The most commonly used intracanal medicament is Ca(OH)2 because it is effective against the majority of endodontic pathogens.[15] However, prior to definite obturation of the root canal, Ca(OH)2 medicament should be removed completely in order to provide maximum interface between the root canal wall and filling material. Previous studies reported that residual Ca(OH)2 on the root canal wall could influence the penetration of sealer into dentinal tubules,[16] reduce the bond strength of a resin-based sealer,[17] and interfere with the sealing ability of a silicon-based sealer.[18]

Various methods have been used to investigate the amount of residues on the canal walls, such as the uses of digital photographs, stereo microscopes, scanning electron microscopes, microtomography computed tomography (micro-CT), and spiral CT.[919202122] In our study, scanning electron microscopy was used at 1,000× magnification, and the remnants of Ca(OH)2 on root canal walls were evaluated using a scoring method similar to that used in previous studies.[91119]

NaOCl irrigation without activation was reported to be an inadequate method for the removal of Ca(OH)2 from the root canals because of limited ability to dissolve inorganic materials.[923] Margelos et al.,[23] showed that using 15% EDTA solution or NaOCl alone as irrigants does not remove Ca(OH)2 efficiently from the root canal; however, the combination of two irrigants with hand instrumentation improves the removal efficiency. Therefore, in the current study, we purposed to evaluate the efficacy of different irrigant agitation protocols using with NaOCl on removal of Ca(OH)2 from root canals.

Result obtained in the present study showed that least efficient was syringe irrigation for Ca(OH)2 removal. This data is in agreement with previous studies.[91924] Additionally, in Group 1, NaOCl was delivered to the root canal by 27-gauge irrigation needle. The syringe needle irrigation may be effective in cleaning the coronal third of root canal but not in the apical third since the irrigant can progress only 1 mm further from the tip of the needle.[25] Therefore, adequate delivery of the irrigant to the WL with needle irrigation may not be obtained.[26] This could be another reason for less removal of Ca(OH)2 from the apical part of the root canal in Group 1.

Limited comparable data is available about the use of CanalBrush for Ca(OH)2 medicament removal.[2027] These studies reported that CanalBrush was not effective in the removal of Ca(OH)2 due to its packing effect. The result of the present study is in agreement with these previous studies. The apical third of the root canals in Group 2 (CanalBrush) showed higher average scores with significant differences compared to apical negative pressure irrigation and sonic agitation groups. CanalBrush did not remove Ca(OH)2 from the apical third, but conversely packed the Ca(OH)2 to the apical part of the canals.

In our study, CanalBrush tip was fractured in the apical third of one specimen like in a previous study. Since the CanalBrush is radiolucent and impossible to discern in radiographs, in the presence of fractured tip, there is a chance of pushing it through the apical foramen with files during the root canal instrumentation.[28]

In all groups, the coronal third demonstrated significantly better results in the removal of Ca(OH)2 than apical third. Lee et al.,[29] reported that this result may be related with the higher velocity and volume of irrigant flow created at the coronal part of the root canal during irrigation procedure. In all of the experimental groups, a statistical difference in cleanliness was observed between the coronal versus apical third, except in Group 4. In the sonic agitation SAF group, no statistical difference was found between the apical and coronal thirds.

The results of the present study showed better efficacy of EndoVac and SAF groups compared with other groups in the apical of the root canal. This could be attributed to the design and working properties of this systems. The SAF is a hollow file which allows for the continuous irrigation of the root canal throughout the procedure, with additional activation of the irrigant by its vibrating motion that creates turbulence in the root canal.[14] In the present study, SAF was used at full WL. Thus, it allows for the delivery of the irrigant to WL and provides constant irrigant turnover at apical third.[30] According to the results of the present study, the use of SAF, in continuous flow with vibrating motion and effective replacement of NaOCl in the apical part of the canal, may provide efficient removal of Ca(OH)2 from apical part of the canal.

The EndoVac system was introduced newly; and to our knowledge, no study has evaluated Ca(OH)2 removal efficacy. EndoVac is a negative pressure irrigation system that has been designed to deliver irrigants safely into the apical portion of the canal in order to optimize the removal of the smear layer and minimize the extrusion of solution through the apical foramen.[13] The placement of the microcannula to WL as recommended by the manufacturer enables the irrigant to penetrate almost to the WL, to be suctioned in sufficient volume, and flow to remove smear layers and displace debris. In our study, the effectiveness of EndoVac on removal of Ca(OH)2 from apical third is related with its better mechanical flushing action and vacuum aspiration effect. Additionally, the orifices of the microcannula may provide a portal of exit for Ca(OH)2, resulting in effective removal from apical third of root canal.

In the present study, even with the use of different irrigant agitation protocols complete removal of Ca(OH)2 was not possible in the apical third of the root canal. This could possibly be due to the nature of dentinal tubules which are irregular and less in number. Whittaker and Kneale[31] also suggested relatively fewer dentinal tubules per unit area being present in the apical third of the root canal wall.

CONCLUSION

Within limitations of this study, we showed that all irrigant agitation techniques were equally effective in removing Ca(OH)2 from the coronal third of the root canal. However, in the apical third of the root canal, present study demonstrated that none of the methods completely removed Ca(OH)2 from the canal walls. SAF and EndoVac showed significantly better performance in removing Ca(OH)2 from apical third of the root canals compared with CanalBrush. The SAF showed similar efficiency in the coronal and apical thirds of the specimens.